Magnetic relay members with grain of the material extending longitudinally thereof

ABSTRACT

A relay including an armature moving in a gap between pole pieces in which the grain of the material of the pole piece and armature extends to the surfaces at the gap to reduce reluctance, a contact carrier being secured to the armature by tabs twisted to overlap the flanges on the contact carrier, the armature being mounted on journals formed from brackets at the ends of the armature, with the journals being produced by reducing the material in thickness locally and deforming it outwardly into a die complementary to the contour of the journal. An insulator is retained at one end of the armature assembly by a wedge-shaped projection on the contact carrier that is received in an opening in the insulator. An arc barrier for the stationary contacts has slots that receive the contact shanks and a transverse wall having an opening between the contacts so that flow of gas is induced to suppress an arc between the contacts as the armature is actuated.

t9 States Patent 1 Tichy [111 3,745,4 [4 1 July 10, 1973 3,317,871 3,470,510 9/1969 Richert 3,621,419

MAGNETIC RELAY MEMBERS WITH GRAIN OF THE MATERIAL EXTENDING LONGITUDINALLY THEREOF Inventor: Melvyn R. Tichy, Brea, Calif.

Assignee: The Deutsch Company, Electronic Components Division, Banning, Calif.

Filed: Apr. 26, 1972 Appl. No.: 247,890

Related US. Application Data Division of Ser, No. 91,005, Nov. 19, 1970, Pat. No. 3,688,230.

US. Cl. 335/230, 335/281 Int. Cl. H01f 7/08 Field of Search 335/229, 230, 234,

References Cited UNITED STATES PATENTS 5/1967 Adams 335/230 335/230 11/1971 Adams 335/230 Primary ExaminerGeorge Harris Attorney-Richard F. Carr [5 7 ABSTRACT A relay including an armature moving in a gap between pole pieces in which the grain of the material of the pole piece and armature extends to the surfaces at the gap to reduce reluctance, a contact carrier being secured to the armature by tabs twisted to overlap the flanges on the contact carrier, the armature being mounted on journals formed from brackets at the ends of the armature, with the journals being produced by reducing the material in thickness locally and deforming it outwardly into a die complementary to the contour of the journal. An insulator is retained at one end of the armature assembly by a wedge-shaped projection on the contact carrier that is received in an opening in the insulator. An arc barrier for the stationary contacts has slots that receive the contact shanks and a transverse wall having an opening between the contacts so that flow of gas is induced to suppress an arc between the contacts as the armature is actuated.

4 Claims, 16 Drawing Figures PATENIE JUL 1 01m SHEEI b [If 4 1 56.5. fla jig/0. I56. 11

MAGNETIC RELAY MEMBERS WITH GRAIN OF THE MATERIAL EXTENDING LONGITUDINALLY THEREOF This is a division of application Ser. No. 91,005, filed Nov. 19, 1970 now U.S. Pat. No. 3,688,230.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention pertains to relays.

2. Description of Prior Art Relays and contactors intended for aerospece and aircraft use increasingly are meeting with requirements for compact size and minimum weight, while conforming to stringent performance specifications. Gravitational, vibrational and other loads imposed on the relays aggravate the design problems. At the same time, there is a need for simplicity of construction to minimize cost, improved reliability and facilitate servicing.

Serious difficulties have been encountered in reconciling all these requirements with existing relay designs. Various portions of these relays have been of relatively complex construction, which has added to their overall size. For example, the pivotal mounting for the armature normally involves a number of separate parts, such as pins, balls or extra fasteners, to be secured to the armature and supporting members in producing a suitable rotational mounting for the armature, all of these parts contributing to the size and weight of the finished relay. The assembled parts introduced an accumulation of tolerances which can cause problems in assembly and operation. Separate fasteners also are needed in securing the contact carrier to the armature. Where there are adjacent pairs of stationary contacts, an arc barrier is required to prevent an arc from being produced across these contacts. Conventionally, this is accomplished by means of a wall of dielectric material positioned between the adjacent contacts. Again, this must be at a sacrifice of weight and volume.

A common type of relay includes a pair of pole pieces which have overlapping spacedfangularly bent, generally parallel end portions. The sidewalls of these pole piece ends define the gap within which the armature moves. There is a relatively high reluctance at the gap where the flux must move transversely to the grain of the metal of the pole piece in entering the gap. This is because the reluctance is greater transverse to the grain than it is longitudinally with respect to the grain. The resulting lack of efficiency at the gap may mean that the permanent magnet and coil must be of greater size in order to produce the necessary force on the armature.

SUMMARY OF THE INVENTION The present invention overcomes the aboveenumerated difficulties, producing a relay that is compact, light in weight and of simple construction. The armature of the relay is pivotally mounted without the use of any extra fasteners or parts. This is accomplished by means of sheet metal brackets which are welded to the opposite edges of the armature, each bracket being provided with an integral journal that fits within an opening in the frame of the relay to pivotally support the armature. A relatively thin-gauge material is used, yet the journal extends outwardly from each bracket a distance greater than the thickness of the material. This is accomplished by a process by which, first, there is an opening formed in the sheet metal bracket, after which the material is coined to reduce its wall thickness around the opening. Then it is progressively bent outwardly on one side to define the journal, in all instances being fully supported on the side to which the material is bent. The material may be forced initially into a generally conical recess in the supporting tool as it is gradually bent to its cylindrical shape. The final tool for forming the journal includes a cylindrical recess of controlled dimension, with a cylindrical punch being driven through the opening in the workpiece to force it into the cylindrical recess.

The contact carrier of dielectric material fits on a plate that is brazed to the top of the armature. This plate along its opposite edges includes a plurality of upwardly projecting, substantially L-shaped tabs. These tabs are twisted inwardly to position their lateral legs over opposite flanges on the base of the contact carrier. The twisting of the upstanding legs of the tabs as this is accomplished causes them to be foreshortened so that the lateral portions of the tabs then exert a compressive force on the flanges of the contact carrier, securely and firmly holding the contact carrier against the armature. The tabs may be bent back away from the flanges to permit removal of the contact carrier, and the contact carrier subsequently may be secured again by retwisting of the tabs. Several cycle are possible without experiencing any fatigue failure.

At one end of the contact carrier is an insulating disk which fits between the contact carrier and the armature bracket to block current flow in that direction. This insulator takes a minimal amount of room, and is permanently installed without the use of separate fasteners. This is accomplished by the use of a wedge-shaped pro- 3 5 jection on the end of the contact carrier adjacent the armature bracket, while the insulator has a rectangular opening in its wall that is adapted to receive the wedgeshaped projection. The insulator is installed by pushing it downwardly into the space between the contact carrier and the bracket, with the projection deflecting the insulator until the opening is reached, at which point it snaps inwardly beneath the shoulder of the wedgeshaped projection and is effectively secured in place.

The arc barrier for the stationary contacts of the relay includes a transverse wall which is provided with parallel slots that receive the shanks of the stationary contacts, which are positioned beneath the header. A side wall extends around three sides of the transverse wall, and projects upwardly beyond it to engage the undersurface of the header. Tapered extensions project downwardly from the transverse wall to facilitate the entry of the contact shanks into the slots. A press fit is provided between these projections and the sidewalls with respect to the contacts and the header, so that there is a frictional force to retain the contact barrier in place.,Also, there are protrusions on the sides of the slots which fit around the shanks of the contacts to assist in holding the contact barrier in place.

Between the contacts, the transverse wall of the arc barrier includes an opening. When the movable contacts are actuated by the armature, the contact support induces a flow of gas through the opening, which forces the arc out away from the space between the contacts and prevents an are from bridging across between the contacts. This gas is pulled from the vicinity of the header and is relatively cool because the header acts as a heat sink. Thus, no dielectric barrier wall is necessary as in conventional designs, and the size of the relay may be reduced accordingly.

The pole pieces of the relay have angled ends, yet provide a low-reluctance flux path to increase the efficiency of the relay. This is accomplished by producing the pole piece from a flat part of magnetic metal which is arranged with the grain of the metal extending from one edge to the opposite edge. The part then is bent intermediate these edges to define the shape of the angled pole piece end. After this, the angled end part is cut at an acute angle with respect to the longitudinal axis between the edges so that the grain of the material runs out to the edge of the pole piece where the out has. been made. Therefore, the flux readily flows in the direction of the grain of the metal to the end of the pole piece and into the gap, with the reluctance being minimized at that location. High-reluctance flux movement across the grain of the metal is avoided. One edge of the armature similarly is cut to provide a surface offering a low-reluctance path to an adjacent pole piece.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective exterior view, partially broken away, of the relay of this invention;

FIG. 2 is a sectional view taken along line 22 of FIG. 3;

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2;

FIG. 4 is an explded perspective view of the relay;

FIGS. 5, 6 and 7 are side elevational views illustrating the way in which a pole piece is formed;

FIGS. 8, 9, 10 and 11 are sectional views showing how the journals for the armature are produced;

FIG. 12 is an enlarged sectional view of the attachment of the contact carrier to the armature;

FIG. 13 is a fragmentary exploded perspective view of one end of the contact carrier and its insulator;

FIG. 14 is a perspective view of the arc barrier;

FIG. 15 is a sectional view taken along line l5--15 of FIG. 2;. and

FIG. 16 is a sectional view taken along line 16-16 of FIG. 15.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The relay or contactor of this invention is contained within a housing or can 8 which is hermetically sealed. After the components have been assembled within the can 8, preferably the air is removed from within, and it is back-filled with gas, such as dry nitrogen, which tends to suppress arcing.

The overall arrangement of the motor of the relay is conventional, including in the embodiment illustrated a pair of coils 9, the ends of the cores 10 of which connect to pole pieces 11 and 12 (see FIGS. 2, 3 and 4). The pole piece 11 is generally L-shaped, having an upper end 13 which is inclined inwardly back over the coils 9 and is provided with a flat horizontal upper surface 14 that is normal to the verticalleg of the pole piece. The upper surface'14 and the opposite surface '15 converge toward the edge so that this portion of the pole piece tapers in thickness. The other pole piece 12 also is L-shaped, with a generally similar upper portion 16 that extends farther over the coils 9 and also has a relatively wide flat upper surface 17.

Engaging the outer surface of the bottom part of the pole piece 11 is a permanent magnet 18 which on its opposite side is engaged by another L-shaped pole piece 19. The latter pole piece has an upper end portion 20 which is inclined inwardly in a spaced relationship over the upper portion 13 of the pole piece 11. This defines a gap 21 between the ends 13 and 20 of the pole pieces 11 and 19, respectively.

The armature 22 is pivotal about its midportion, as explained more fully below, and in the de-energized position the beveled edge surface 23 of the armature 22 engages the lower surface 24 of the end portion 20 of the pole piece 19. When the relay is energized, the armature 22 is rotated counterclockwise from the position shown in FIG. 2, so that its undersurface 25 engages the upper surface 14 of the end portion 13 of the pole piece 11.

In the de-energized position of the relay, the flux from the permanent magnet 18 flows as indicated by the solid-line arrows in FIG. 2, holding the armature in the position shown. Thus, the circuit from the permanent magnet 18 includes the pole piece 19, from the upper portion 20 of which the flux is conducted into the armature 22 and then into the upper portion 16 of the pole piece 12. The cores .10 of the coils 9 conduct the flux back to the opposite pole of the permanent magnet 18.

When the coils are energized, they create a flux indi cated by the phantom-line arrows (see FIG. 2) which opposes the flux of the permanent magnet. Ultimately, sufficient force is created across the gap 21 to cause the armature 22 to pivot away from the surface 24 of the pole piece 19 into engagement with the surface 14 of the pole piece 11.

The pole pieces are constructed in a way which minimizes reluctance, thereby resulting in increased forces on the armature. ln producing the pole piece 1 l, for example, the procedure shown in FIGS. 5, 6 and 7 is followed. First, a flat strip of magnetic material 11a is given a thickness and a width corresponding to that of the pole piece 11. In preparing the workpiece 11a, it is arranged so that the grain of the metal extends between the opposite edges 26 and 27. In other words, as the metal piece 11a is shown in FIG. 5, the grain runs vertically and is perpendicular to the upper and lower edges 26 and 27. Next, the piece is bent to the position of FIG. 6 so that its end portion is at the angle of the surface 15 of the completed pole piece. When this bend is made, the grain of the metal extends around the corner that is formed. After this, the upper bent portion is cut on the outside, removing enough material to complete the formation of the pole piece and define the surface 14. This cut is at an acute angle to the longitudinal axis between the edges 26 and 27, so that the grainof the metal runs out to the surface 14, which forms one side of the gap 21 within which the armature operates.

The reluctance of the metal is less in the direction of its grain than in any other direction though the pole piece. Therefore, in the present instance, the magnetic flux can flow through the pole piece 11 with minimum reluctance from the attachment of the cores 10 to the end surface 14. There, the flux can enter the gap 21 by continuing to flow in the path with the grain of the metal. It is not necessary for the flux to flow in a direction transverse to the grain when leaving the pole piece 12. Therefore, by bending the metal piece and then making a cut in the bent portion in forming the pole piece, reluctance is minimized and the efficiency of the relay is improved.

The pole pieces 12 and 19 are formed similarly. For the pole piece 12, the cut is made in the bent portion 16 along the top surface 17 so that there is a lowreluctance path for flux between the overhanging portion of the armature and the pole piece. The cut is made on the top part of the bent end portion 20 of the pole piece 19, so that its surface 24 is parallel to the grain of the material and reduces the reluctance at gap 21 between the armature 22 and pole piece 11.

In the armature 22, the grain of the metal runs across from the beveled edge 23 to the opposite edge 27a. At the gap 21, therefore, the reluctance is minimized where the flux enters and leaves the armature at the edge 23.

The armature 22 includes central extensions 28 and 29 at its opposite ends to which are spot-welded upstanding brackets 30 and 31 (see FIGS. 3 and 4). Tubular journals 32 and 33 extend outwardly from the upper portions of the brackets 30 and 31 and are received within openings 34 and 35 in supports 36 and 37 that extend upwardly from side plates 38 and 39 of the relay frame. Thrust washers 40 and 41 are interposed between the brackets 30 and 31 and the supports 36 and 37 of the frame members 38 and 39.

The journals 32 and 33 are integral with the brackets 30 and 31, yet each extends outwardly in the axial direction a distance greater than the thickness of the material from which the brackets are made. This is made possible through the procedure illustrated in FIGS. 8, 9, l0 and 11. First, an opening 42 is formed in the sheet metal piece of the bracket, the diameter of the opening being at a 1:1 ratio with respect to the thickness of the material. Next, as shown in FIG. 9, a flat-ended tool 43 is forced against the workpiece around the opening 42 on one side of the workpiece, while a flat die 44 backs up the material on the other side. As a result, the material of the workpiece is coined and reduced in thickness. The diameter of the opening 42 becomes smaller as the material is displaced and the wall thickness is decreased. Following this, as shown in FIG. 10, a punch 45 is driven against the workpiece adjacent the opening 42, this tool having a generally conical end part 46. At the same time, on the opposite side of the workpiece a stationary die 47 backs up the material. The die 47 includes a frustoconical recess 48 of controlled shape corresponding to the protrusion 46 on the punch 45. After this, as indicated in FIG. 11, the journal is completed by driving a cylindrical punch 49 thoughthe opening 42, spreading the material outwardly and enlarging the opening. Again, the backside of the material is supported, this time by a die 50 having an opening 51 generally complementary to the punch 49, as well as a counterbore 52 that corresponds in diameter to the desired outside diameter of the journal.

Thus, by gradually reducing the thickness of the material as it is deflected outwardly in producing the journal, it is possible to obtain the relatively long projection for the journal as well as producing a journal of precise dimension. It is important in accomplishing this that the backside of the material be supported at all times as the forming takes place, the outside dimension being controlled rather than the inside dimension. It may be desirable to produce the journal in more steps than illustrated to more gradually deflect the material to its final configuration. The general procedure, however, will be the same as illustrated.

The resulting construction provides a simplified and very compact mounting arrangement for the armature. The conventional assembly of parts for mounting the armature is replaced with a single element at either end of the armature. By eliminating parts, tolerances also are eliminated and greater precision of fit can be obtained. In other words, there can be no accumulation of tolerances to create an error. The construction is of minimum size in providing an armature pivot resulting in a maximum dimension on the armature for supporting and holding the contact carrier.

A thin plate 54 is spot-welded and than brazed to the upper surface of the armature 22, extending from one end to the other at the central portion of the armature. A series of openings 55 through the plate 54 provides locations for the brazing and permits visual inspection of the attachment. A plurality of L-shaped tabs 56 extends upwardly from either side edge of the plate 54. Positioned on the plate 54 is a contact carrier 58 of dielectric material. This member has an elongated flange 59 along either side edge, extending for the full length of the contact carrier. The attachment of the contact carrier 58 to the armature is accomplished by twisting the tabs 56 inwardly so that their upper legs 61 overlie the flanges 59 (see FIG. 12). As this is done, the vertical legs 62 of the tabs become foreshortened because of the twisting, and the upper legs 61 press inwardly on the flanges 59. The result is a secure attachment of the carrier 58 to the armature 22 without the use of rivets or other fasteners. The attachment is releasable by returning the tabs 56 to their original positions. There may be several cycles of removal and installation of the contact carrier 58 without encountering fatigue of the tabs 56.

Near one end of the contact carrier 58 is a raised portion 63, upon which is a reed 64 having transverse supports 65 at its outer ends which carry pairs of contacts 66 and 67. A buffer plate 68 is on top of the reed 64 and rivets 69 are used in attaching the reed to the carrier 58.

In the embodiment shown, additional contacts 71 and 72 are carried by reeds 73 which are secured to the carrier 58 near its opposite end. This end of the contact carrier 58 is very near the bracket 31 because of the compact nature of the relay. With the bracket 31 being at ground potential, the contacts 71 and 72 on the reeds 73 must be insulated from the bracket 31. This is accomplished by a flat sheet 74 of dielectric material having a rounded upper edge and a square opening 75 extending througn it. On the end of the carrier 58 is a wedge-shaped projection 76 having its tapered surface upwardly and a righbangled shoulder 77 along its lower edge (see FIGS. 3 and 13). The insulator 74 is installed simply by pushing it downwardly along the end of the carrier 58, which causes its bottom edge to be pried outwardly by the wedge-shaped projection 76. As soon as the opening 75 is reached, however, the projection enters the opening 75, and the shoulder 77 becomes positioned at the bottom edge of the opening. This locks the insulator 74 in position, preventing its removal. The result is a simple means of holding the insulator'74 in place, occupying a minimum amount of space and contributing to the overall compactness of the relay.

Positioned above the carrier 58 is a header 78, which is held to the relay frame by brackets 79 and 80. The bracket 79 is attached to the side of the plate 38 of the relay frame by means of screws extending through openings 82 in the bracket 79 and received in tapped holes 83 in the plate 38, as seen in FIG. 1. A screw 81 is extending through the opening 84 in the bracket 80 to similarly secure it to the side plate 39 of the frame.

Depending from the header 78 are pairs of contacts 85 and 86 which are adapted to be engaged by the contacts 66 and 67 that move with the armature. The contacts 85 include enlarged lower end portions 87 at the ends of cylindrical shank portions 88 that extend downwardly through the header 78. Similarly, the contacts 86 have enlarged lower end portions 89 and cylindrical shanks 90. This positions the enlarged contact portions 87 and 89 at a location below and parallel to the header 78. In the de-energized position of the relay, as shown in FIG. 2, the contacts 66 engage the ends of the contacts 85, while contacts 67 and 86 are separated. Rotation of the armature 22 to the energized position breaks the circuit between the contacts 66 and 85, while bringing the contacts 67 and 86 into engagement.

Associated with the contacts 85 and 86 beneath the header 78 are are barriers 91 of dielectric material, best seen in FIGS. 2, 4, and 16. Each of the arc barriers 91 includes a U-shaped sidewall 93,adjacent but below the upper edge 94 of which is a transverse wall 95. Two parallel slots 96 extend inwardly from the outer edge 97 of the wall 95 and terminate at semicircular inner ends 98. Adjacent the inner ends are semicylindrical protrusions 99, which extend perpendicularly to the wall 95. An opening 100 extends through the wall 95 between the slots 96. Outwardly of the opening 100, at the forward edge 97 of the wall 95 and between the slots 96, is an upward projection 101. The upper edge of the projection 101 is in the same plane as the upper edge 94 of the U-shaped sidewall 93. The wall 95 is provided with downward extensions 102 around the peripheries of the slots 96. The extensions 102 incline away from the surface of the wall 95 from the outer edge 97 to the semicircular inner peripheries 98 of the slots. In other words, the extensions 102 are tapered, increasing in dimension from the edge 97 to the slot ends 98.

When the arc barriers 91 are installed, the shanks 88 and 90 of the contacts 85 and 86 fit within the slots 96 at their inner ends 98 with which they are substantially complementary. This positions the shanks 88 and 90 just inwardly of the projections 99, which thereby hold the shanks in the inner ends of the slots. The material of the arc barriers 91 is deflected as the shanks 88 and 90 of the contacts 85 and 86 are moved into the inner portions of the slots.

In addition, the enlargements 87 and 89 at the. bottom ends of the shanks 88 and 90 fit beneath the downward extensions 102 of the arc barriers. An interference fit is provided so that the arc barriers exert a resilient force against the contact enlargements 87 and 89 and the undersurface-of the header 78. The arc barriers are deflected slightly as the enlargements 87 and 89 of the contacts 85 and 86 move along the tapered outer portions of the extensions 102 of the slots 96. the tapered configuration of the extensions facilitates movement of the arc barriers into position so that the resilient force can be exerted.

This, together with the protrusion 101 on the upper surface of the wall 95, causes the arc barriers 91 to be frictionally retained to the header 78 and the contacts, and to be firmly locked into position against movement. At the same time, the arc barriers are readily removable when needed. Both the attachment and removal of the arc barriers 91 are facilitated by the facts that no fasteners are required and that the device automatically locks in place when slid onto the contacts at the base of the header.

The arc barriers 91 accomplish their function of preventing arcing between the adjacent pairs of stationary contacts and 86 by inducing a flow of gas between the contacts of each pair as the moving contacts are separated from them. Thus, when the relay is moved from the de-energized position of FIG. 2 to the energized position, the movement of the reed 64 and the support 65 for the contacts 66 causes the gas within the can 8 to flow through the opening in the adjacent arc barrier 91. This pulls a column of the gas between the two stationary contacts 85, preventing an arc from bridging between them. The movement of the gas will blow out any are that tends to occur, forcing the arc outwardly rather than inwardly between the adjacent contacts. The gas is drawn from the vicinity of the header 78, which functions as a heat sink so that the gas is relatively cool and more effectively accomplishes the arc suppression. The are barriers operate, therefore, by creasting a flow of gas, rather than utilizing a dielectric barrier as in conventional designs. This permits the contact pairs to be positioned closer together than where a dielectric barrier is employed, which, in turn, allows the relay to be made more compact.

The foregoing detailed description is to be clearly understood as given by way of illustration and example only, the spirit and scope of this invention being limited solely by the appended claims.

I claim: 1. An electric motor device comprising a duality of pole pieces,

said pole pieces having adjacent end portions in spaced relationship to define a gap therebetween, means for producing flux across said gap, and an armature,

said armature having a portion in said gap, said armature being movable between a first position in which said portion of said armature engages said end portion of one of said pole pieces, and a second position in which said portion of said armature engages said end portion of the other of said pole pieces,

said end portion of said one pole piece at said gap being at an angle with respect to the remaining portions of said one pole piece, said end portion of said one pole piece having a first surface for engagement by said armature, and a second surface opposite thereto, said first and second surfaces converging toward said end of said one pole piece, said first surface being at an acute angle with respect to the direction of the grain of the material of said one pole piece for thereby extending across said grain and providing a low-reluctance flux path into said gap. 2. A relay comprising v a first pole piece, a second pole piece,

said first and second pole pieces having opposed end portions defining a gap, means for creating a magnetic flux across said gap.

an armature having an edge portion, and means mounting said armature for movement between a position of engagement between said edge portion of said armature and said end portion of said first pole piece, and a position of engagement between said edge portion of said armature and said end portion of said second pole piece, said armature being of magnetic metal the grain of which extends longitudinally to said edge portion, said edge portion including a first surface on one side thereof for engagement with said end portion of said first pole piece, said first surface being convergent outwardly with respect to the opposite side of said armature, said first surface extending across said grain for reducing the reluctance at said first surface. 3. A device as recited in claim'2 in which said end portion of said second pole piece has an outer edge, said second pole piece being made of magnetic metal the grain of which extends longitudinally to said outer edge,

said outer edge of said second pole piece including a first surface on one side thereof for engagement with said edge portion of said armature, said first surface of said outer edge of said second pole piece being convergent outwardly with respect to the opposite side thereof and extending across said grain of said second pole piece for reducing the reluctance at said first surface of said outer edge of said second pole piece. 4. A pole piece for an electric motor device comprising a piece of magnetic material arranged with its grain running from one edge to the opposite edge thereof, said piece of magnetic material being bent intermediate said edges thereof, one end portion of said piece of magnetic material tapering in thickness toward the outer edge thereof so as to present an elongated surface which is substantially transverse to said grain and is adapted to be placed in juxtaposition with an armature. 

1. An electric motor device comprising a duality of pole pieces, said pole pieces having adjacent end portions in spaced relationship to define a gap therebetween, means for producing flux across said gap, and an armature, said armature having a portion in said gap, said armature being movable between a first position in which said portion of said armature engages said end portion of one of said pole pieces, and a second position in which said portion of said armature engages said end portion of the other oF said pole pieces, said end portion of said one pole piece at said gap being at an angle with respect to the remaining portions of said one pole piece, said end portion of said one pole piece having a first surface for engagement by said armature, and a second surface opposite thereto, said first and second surfaces converging toward said end of said one pole piece, said first surface being at an acute angle with respect to the direction of the grain of the material of said one pole piece for thereby extending across said grain and providing a low-reluctance flux path into said gap.
 2. A relay comprising a first pole piece, a second pole piece, said first and second pole pieces having opposed end portions defining a gap, means for creating a magnetic flux across said gap. an armature having an edge portion, and means mounting said armature for movement between a position of engagement between said edge portion of said armature and said end portion of said first pole piece, and a position of engagement between said edge portion of said armature and said end portion of said second pole piece, said armature being of magnetic metal the grain of which extends longitudinally to said edge portion, said edge portion including a first surface on one side thereof for engagement with said end portion of said first pole piece, said first surface being convergent outwardly with respect to the opposite side of said armature, said first surface extending across said grain for reducing the reluctance at said first surface.
 3. A device as recited in claim 2 in which said end portion of said second pole piece has an outer edge, said second pole piece being made of magnetic metal the grain of which extends longitudinally to said outer edge, said outer edge of said second pole piece including a first surface on one side thereof for engagement with said edge portion of said armature, said first surface of said outer edge of said second pole piece being convergent outwardly with respect to the opposite side thereof and extending across said grain of said second pole piece for reducing the reluctance at said first surface of said outer edge of said second pole piece.
 4. A pole piece for an electric motor device comprising a piece of magnetic material arranged with its grain running from one edge to the opposite edge thereof, said piece of magnetic material being bent intermediate said edges thereof, one end portion of said piece of magnetic material tapering in thickness toward the outer edge thereof so as to present an elongated surface which is substantially transverse to said grain and is adapted to be placed in juxtaposition with an armature. 